Peng Xiaoli, Chang Hui, Gu Yeyun, Chen Junli, Yi Long, Xie Qi, Zhu Jundong, Zhang Qianyong, Mi Mantian
Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China. Department of Public Health, School of Preclinical Medicine, Chengdu Medical College, Chengdu, China.
Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China.
Cancer Prev Res (Phila). 2015 Jun;8(6):509-17. doi: 10.1158/1940-6207.CAPR-14-0357. Epub 2015 Mar 17.
Our previous study selected a promising chemopreventive agent 3,6-dihydroxyflavone (3,6-DHF) and found that 3,6-DHF significantly upregulates miR-34a and downregulates miR-21 in breast carcinogenesis, yet the upstream and downstream events of the anticancer mechanism remain unclear. The present study showed that 3,6-DHF cotreatment effectively inhibits carcinogens-induced breast carcinogenic transformation in human breast epithelial MCF10A cells. The data revealed the significant downregulation of miR-34a and upregulation of miR-21 in breast carcinogenesis, which could be mitigated by 3,6-DHF treatment. Methylation-specific PCR detections showed that 3,6-DHF inhibits the hypermethylation of the miR-34a promoter. Further studies indicated that 3,6-DHF is an effective methyltransferase (DNMT)1 inhibitor, docking to the putative cytosine pocket of the protein, and thus decreases the DNMT activity in a dose-dependent manner. Moreover, the ChIP-qPCR analysis for histone modifications showed that 3,6-DHF treatment significantly lowers the H3K9-14ac on the miR-21 promoter. In addition, our study revealed that 3,6-DHF represses the PI3K/Akt/mTOR signaling pathway in breast carcinogenesis in vitro and in vivo. Inhibition of miR-34a or overexpression of miR-21 significantly reduced the effects of 3,6-DHF on Notch-1 and PTEN, and consequently weakened the suppression of 3,6-DHF on PI3K/Akt/mTOR. We concluded that 3,6-DHF upregulates miR-34a via inhibiting DNMT1 and hypermethylation, whereas downregulates miR-21 by modulating histone modification, and consequently suppresses the PI3K/Akt/mTOR signaling pathway in breast carcinogenesis.
我们之前的研究筛选出了一种有前景的化学预防剂3,6 - 二羟基黄酮（3,6 - DHF），并发现3,6 - DHF在乳腺癌发生过程中显著上调miR - 34a并下调miR - 21，但其抗癌机制的上下游事件仍不清楚。本研究表明，3,6 - DHF联合处理可有效抑制致癌物诱导的人乳腺上皮MCF10A细胞发生乳腺癌转化。数据显示，在乳腺癌发生过程中miR - 34a显著下调，miR - 21上调，而3,6 - DHF处理可缓解这种情况。甲基化特异性PCR检测表明，3,6 - DHF抑制miR - 34a启动子的高甲基化。进一步研究表明，3,6 - DHF是一种有效的甲基转移酶（DNMT）1抑制剂，可与该蛋白假定的胞嘧啶口袋结合，从而以剂量依赖的方式降低DNMT活性。此外，针对组蛋白修饰的ChIP - qPCR分析表明，3,6 - DHF处理可显著降低miR - 21启动子上的H3K9 - 14ac。另外，我们的研究表明，3,6 - DHF在体外和体内均可抑制乳腺癌发生过程中的PI3K/Akt/mTOR信号通路。抑制miR - 34a或过表达miR - 21可显著降低3,6 - DHF对Notch - 1和PTEN的作用，从而削弱3,6 - DHF对PI3K/Akt/mTOR的抑制作用。我们得出结论，3,6 - DHF通过抑制DNMT1和高甲基化上调miR - 34a，而通过调节组蛋白修饰下调miR - 21，从而在乳腺癌发生过程中抑制PI3K/Akt/mTOR信号通路。
